POCOP

POCOP
Names
IUPAC name
1,3-bis((diphenylphosphino)oxy)benzene
Other names
Resorcinolbisphosphinite
Identifiers
3D model (JSmol)
ChemSpider
Properties
C30H24O2P2
Molar mass 478.47 g·mol−1
Appearance yellow solid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

POCOP is a popular type of pincer ligand. Pincer type ligands are tridentate ligands that bind three sites on one plane of a metal complex. POCOP forms complexes with one M-C(aryl) bond and two phosphinite ligands.[1] The term POCOP is used both for the ligand, with formula C6H4(OPPh2)2, and its complexes, with formula C6H3(OPPh2)2]− (Ph = C6H5)

Synthesis and Structure

Interest in POCOP arises from its easy synthesis, which accommodates many substituents on phosphorus and results in higher yields than other PCP analogues.[2] The parent POCOP ligand is prepared by treating resorcinol with chlorodiphenylphosphine:[3]

C6H4(OH)2 + 2 ClPPh2 → C6H4(OPPh2)2 + 2 HCl

Related ligands can be prepared from chlorodiisopropylphosphine.

Structure of a Ni(POCOP)X complex.

Representative complexes are of the type Ni(POCOP)X (X = halide, alkyl, thiolate). The halides arise by direct reaction of the ligand and a nickel halide and offer a relatively cheap, nontoxic and readily available option of the ligand for various applications.[4] There can also be variable conformations of POCOP pertaining to the various R groups branching off of the donor atoms.

Thermal Ellipsoid plot of Ni(POCOP)Cl compound.

In most cases the MPOCOP center features a planar MC3O2P2 core. The rigid conformation and square planar geometry of the POCOP ligand allow for systematic changes over the steric and electronic environment at the metal center.[2] The geometry of metal compounds formed with POCOP ligands can be seen through the P-Ni-P (164.01 Å ) and C-Ni-Cl(178.31Å) bond angles found for (POCOP)NiCl. The bond angles of this compound are representative of angles found for several other pocop metal compounds.[4] Because of relatively small P-Ni-P bond angle the otherwise Ni complexes exhibit a slight tetrahedral distortion.

Catalytic reaction

Pincer ligands participate in a variety of organic transformation, such as the hydrosilylation, and ethylene oligomerizations, and homocoupling of benzyl halides. I.[5] Ni PCP pincer complexes promote sulfur-carbon forming reactions.[2]

References

  1. ↑ Morales-Morales, David; Jensen, Craig (2007), The Chemistry of Pincer Compounds, Elsevier, ISBN 978-0-444-53138-4
  2. 1 2 3 Morales-Morales, D. Pincer Complexes. Applications in Catalysis. Rev. Soc. Quím. Méx. 2004, 48, 338-346
  3. ↑ R. B. Bedford, S. M. Draper, S. P. Noelle and S. L. Welch, "Palladium bis(phosphinite) 'PCP'-pincer complexes and their application as catalysts in the Suzuki reaction", New J. Chem. 2000, 24, 745-747.doi:10.1039/B004793G
  4. 1 2 Pandarus, V; Zargarian, D (2007), "New Pincer-Type Diphosphinito (POCOP) Complexes of Nickel", Organometallics, 26 (17): 4321–4334, doi:10.1021/om700400x
  5. ↑ Chen, Tao, Limin Yang, Liang Li, and Kuo-Wei Huang. "Homocoupling of Benzyl Halides Catalyzed by POCOP nickel Pincer Complexes." Tetrahedron 68 (2012): 6152-157
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